Abstract
This thesis presents a series of studies investigating the mechanisms of various catalytic reactions and metalacyclic complex formation through the use of density functional theory (DFT) calculations. Specifically, the mechanisms of nickel (Ni)/rhodium (Rh)-catalyzed cross-coupling and rhodium-catalyzed olefin hydroboration reactions, as well as rhenium (Re)/tantalum (Ta) metalacyclic complex formation.In Chapter 2, the Ni-catalyzed cross-coupling reaction of 2,2-difluorovinyl benzoate and arylboronic acid was investigated through DFT calculations. It was found that the base exchange step after oxidative addition can facilitate the following transmetalation.
Chapter 3 discussed the Ni-catalyzed asymmetric ring-opening reaction of dinaphthofuran forming C-C. It was discovered that migration of the phenyl nucleophile to the Ni(0) metal center prior to oxidative addition of a C-O bond to Ni(0) plays a significant role in the mechanism for asymmetric selectivity.
In Chapter 4, the mechanisms of Rh(III)-catalyzed intramolecular cross-coupling reaction of two carbon-carbon double bond to form macrocycles was investigated. Theoretical studies revealed that the formation of unobserved olefination macrocyclization product needs to undergo β-H elimination, which requires a high Gibbs energy barrier due to the stabilization of the C-H bond by the electron-withdrawing group (-CF3).
Chapter 5 discussed the mechanisms of Rh-catalyzed regiodivergent hydroboration of alkenes for the synthesis of linear and branched alkylboronates. DFT calculations revealed that the very different steric effects of two ligands are responsible for product selectivity.
In Chapter 6, DFT calculations were performed to study Rh-catalyzed asymmetric hydroboration of silyl enol ethers using two new phosphine ligands to construct valuable chiral boronic esters. The study found that the ligand can create an excellent chiral pocket for the asymmetric hydroboration.
Chapter 7 investigated the reactivity of rhenacyclobutadiene with allenes was studied using DFT calculations. It was found that the initial nucleophilic attack of allenes on either ReC(OR) or ReC(Ar) is important for the product selectivity.
In Chapter 8, the mechanism on reactions of metallacyclobutadienes with aminoalkynes to synthesize Dewar metallabenzenes was investigated with DFT calculations. The mechanism of the reaction and the nature of Dewar metallabenzenes were discussed.
Finally, in Chapter 9, the mechanism for the synthesis of tantallapyridinium complex using tantalum alkyne complexes with isocyanide was studied with the aid of DFT calculations. The tantallapyridinium ring was found to be aromatic based on various experimental and theoretical results.
Overall, this thesis provides valuable insights into the mechanisms of various catalytic reactions and metalacyclic complex formations, which can aid in the development of new catalysts and synthetic method.
| Date of Award | 2023 |
|---|---|
| Original language | English |
| Awarding Institution |
|
| Supervisor | Zhenyang LIN (Supervisor) |
Cite this
- Standard